It is said that if one of these turtles has once begun to lay her eggs in the sand, nothing will induce her to pause in her task until she has finished it, and that even if the eggs are taken away from her as fast as she lays them, she will still go steadily on just as if she were undisturbed. CROCODILES AND ALLIGATORS Of course you know what these huge creatures are like. They are just enormous lizards, fifteen, or twenty, or even thirty feet long, with very short legs, and very clumsy bodies, and very long tails. And their great jaws are armed with rows of most terrible teeth. But what is the difference between crocodiles and alligators? Well, in some ways they are certainly very much alike; but you can always tell them by the shape of their heads, for the muzzle of a crocodile is always narrowed just behind the nostrils, while that of an alligator is not. And in the crocodiles the fourth lower tooth fits into a notch in the edge of the upper jaw, so that you can distinctly see it even when the mouth is closed. All these creatures live in the water, and spend a great deal of their time lying motionless on the surface, when they look like floating logs. One would think that they were fast asleep. But woe betide any animal which comes to drink from the bank close by, for one of the great reptiles instantly dives, swims swiftly along under water, and knocks it into the stream by a blow from its mighty tail. There is scarcely any animal which does not fall a victim at times to these giant lizards. And as soon as the unfortunate creature is knocked into the water it is dragged beneath the surface, and held there until it is drowned. You would think that the reptiles themselves would be drowned, wouldn't you, as they have to remain submerged for many minutes with their jaws widely opened? But they have a very curious valve at the back of the throat, and as soon as the mouth is opened this closes so tightly that not even the tiniest drop of water can find its way down the throat. Both crocodiles and alligators swim with very great speed by waving their powerful tails from side to side in the water. They can run, too, with some little pace upon land. But it is very easy to avoid them, for the bones of their necks are made in such a way that they cannot turn their heads, and all that one has to do if pursued is to spring suddenly to one side. But of course it is necessary to avoid the stroke of the tail. The crocodiles always lay their eggs in the sand on the bank of a river. The eggs are about as big as those of a goose, and are generally buried at a depth of a couple of feet. The mother reptile always sleeps on the top of the nest, and it is said that when the little ones are ready to hatch out they utter a curious little cry. The mother hears this, and scoops away the sand under which they are buried, in order that they may have no difficulty in making their escape.